i keep kois about 1 year now, as i browse through the forum, i think i overstock in my FGT i got 9 gold color, 1 black and 1 silver. all is local kois and i notice some kois cant really grow.... even i feed them aquamaster "growth". is it because of the FGT too small or genetic?i got do water changes every week about 20%

so far i have kept them for 1 year and all are healthy, none of it died before. like what you say, i a bit worry when all grow up and lack of space. can you recommend how many should i keep in a FGT with size 5ft x 3ft x 1.5ft?is the rock no good for kois?

As of the moment you have around maximum of 600 liters of water and that translate to just 60 liters per adult koi. A good stocking level among more experienced hobbyist is around 2000 to 3000 liters per koi. Unless you just do very minimal feeding, the pollution level in the water will still keep on rising even at already 20% water change a week. I have done experiments before growing 10 koi easily in 3000 liter small pond but to maintain good quality water while feeding enough to grow the koi, the system was almost a flowtru system already changing as much as 20 to 40% water a day with lots of filtration and a very high turnover rate. Lets just say it was stressful as one mistake like a power outage is dangerous. In your case, for the size of the FGT and thru minimal feeding its not all bad in order to keep the koi purposely stunted. Do know that allowing all 10 koi to grow above 70cm creates higher risk for the koi.

With regards to the stones at the bottom, normally more experienced hobbyist would not recommend because of 3 reasons. Its hard to get rid of waste. Chances of injury to koi is greater. The stone media is not really as effective media compared to other media. Do take note that when one removes the stone, there is a possibility that trapped waste will release hydrogen sulfide and bad bacteria that may harm your overpopulated stressed koi.

Arrghhh..... i'm very piss off....my kois suddenly got fish lice.... and i read through the forum regarding the treatment is using dimilin and masoten.so i go to yamakoshi mura shop at jalan mount erskine penang to seek help. the girl calculate my total water amount is 500liter and ask her foreigner worker to pack 2 small pack of medicine (dimilin + masoten + forget the name) + 2 pack of 2.5kg salt for 2 times treatment.i go back home put in the 2.5kg salt and waited 20 minutes until it fully dilute. then put half pack of the medicine first and wait 2 hours. all kois are ok and i put the remaining half pack.i went out for 2 hours plus and came home to see that 3 of my kois dead. 1 black, 1 gold butterfly and 1 silver butterfly......

just curious is the foreigner worker put the medicine wrongly into the pack or over dose?

i believe yamakoshi mura shop is professional and thus this things happen to me......